NovemberDecember 2008
If not designed and constructed correctly, masonry (or other) fences and walls can crack, fail, injure or kill, and cause lawsuits.
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Masonry often can be the best choice for fences, freestanding walls, or for walls that retain earth. But if not designed and constructed correctly, masonry (or other) fences and walls can crack, fail, injure or kill, and cause lawsuits. The author’s cases demonstrate repeatedly that all of this bad news would not have occurred if there had been compliance with the building code.
Code Requirements
The International Building Code (IBC) usually is (but not always) the adopted and applicable law for designing and constructing new masonry fences and retaining walls. The IBC also requires the owner to bring existing structures involving safety to current code (IBC 101.3, 102.1, 115.1). Relevant IBC ’06 requirements include (but are not limited to) the following:
Design professional: The code (IBC 106.1) requires plans and specifications by a “registered design professional” for walls and most other structures. For masonry (or other) fences and retaining walls, often only licensed professional engineers (and few of them) are qualified to apply the math, physics, and soil science necessary to assure code compliance. If not done in compliance with code, the risk of wall failure and casualty is so great that the engineer should not only assure proper design but should also inspect construction and existing structures (government inspectors are rarely licensed engineers).
Structure: Walls (and other structures) are required (IBC 1603) to support safely the dead loads from the wall itself, any live loads (e.g. backfill, traffic), and environmental loads such as specified for wind (IBC 1609), rain, snow (IBC 1608), water action, flood (IBC 1612), and earthquake (IBC 1613). The IBC also requires compliance with Building Code Requirements for Masonry Structures (ACI 530), which often requires steel reinforcement.
Foundation: The loads from walls (or other structures) carried to the earth are required (IBC 1804) not to exceed the capability of the earth to support said loads. The allowable vertical and horizontal soil pressure and sliding coefficient of friction for different soil types are in the code (IBC 1804.2), as well as minimum footing depth (IBC 1805.2).
Drainage: Earth adjacent to walls (and other structures) is required to be sloped to drain away (IBC 1803.3). The code (IBC G103.4) prohibits construction that will “increase the design flood elevation more than one foot in the community.”
Retaining walls: In addition to structure requirements (IBC 1603 above), the code (IBC 1806) requires retaining wall design to assure “stability against overturning, sliding, excessive foundation pressure and water uplift” and “a factor of safety of 1.5 against lateral sliding and overturning.” Footing drains behind the wall leading to weepholes through the bottom of wall usually are necessary to reduce hydrostatic pressure.
Case Summaries
In none of the following cases was there any record of the required design or inspection by a licensed professional engineer. A professional engineer could have prevented all of this bad news, including the litigation that followed, by assuring code compliance.
Case #1 Fence Column Death: A masonry fence column lower brick had been knocked out by a vehicle (Photo 1a). Two months later, the column collapsed onto a 5-year-old boy (Photo 1b) who died shortly thereafter of a skull fracture and massive brain hemorrhage. The author found that the cause of the column collapse was missing reinforcing steel and the missing lower brick, each of which did not comply with code. Therefore, the structure was hazardous before the vehicle impact, more hazardous after the impact, and caused the death.
Case #2 Fence Collapse: A masonry fence collapsed on vehicle impact (Photo 2), fortunately without human injury. Fence footing depth and missing reinforcing steel did not comply with code and were causes of the fence collapse.
Case #3 Fence Caused Flood Damage: In violation of code, a masonry wall (Photo 3) backed up the flow of floodwater onto upstream property, damaging buildings and valuable building contents.
Case #4 Retaining Wall Failure: A masonry retaining wall (Photo 4a) violated many code requirements, including inadequate strength of the wall, missing reinforcing steel, inadequate surface drainage behind wall, no footing drain, and no weepholes. These deficiencies caused wall failure (Photo 4b).
